Prince was Scheduled to Meet with Addiction Dr. Day After Death

Prince was supposed to meet with a doctor specializing in addiction treatment the day after he died ... to deal with a "grave medical condition."

Dr. Howard Kornfeld, a national authority on opioid addiction, could not clear his schedule on April 21st, so he sent his son, Andrew, to meet with the singer ... this according to the Star Tribune.

Dr. Kornfeld was supposed to come the following day, and his son -- who works with him at the Recovery Without Walls clinic -- was going to outline the course of treatment. Andrew is the person who called 911 to report Prince was lifeless in the elevator.

According to the report, Dr. Kornfeld was initially contacted by one of Prince's reps, who said the singer "was dealing with a grave medical emergency."